Trunked communication systems are generally known. Such systems are typically used as a primary mode of communication by organizations where mainly short messages are exchanged (e.g., police, firemen, sewer workers, servicemen, etc.).
Trunked radios are typically operated under a simplex format. Under a simplex format a single radio channel is used to both transmit and receive messages.
Radios used in trunked systems are typically associated with talk groups and support talk group calls. In addition, radios used in trunked systems may also support private calls. A talk group is generally defined as a group of users within a certain geographic area or areas and is usually defined by a system operator of the trunked system. For example, a system operator may define a talk group for police officers serving the same geographic area.
Messages between members of a talk group may be accomplished by a user of the radio simply activating a microphone button and speaking into the microphone. Upon activation of the microphone button, the radio transmits a radio identifier and/or talk group identifier to a zone controller. The zone controller identifies the talk group, locates other members of the talk group and retransmits audio to the other members of the talk group as the user begins speaking. Typically this is accomplished by allocating a repeater within each service coverage area in support of the transmission.
While trunking systems work relatively well, they are limited in their ability to operate over multiple zones. Where multiple zones are involved, the channel setup time may be too long and audio information may be lost (also known as “audio truncation”). Accordingly, a need exists for a method and apparatus for setting up trunked calls across multiple zones.